Donald Trump is the most psychologically ill-equipped president in US history, according to former foreign minister Gareth Evans.

Mr Evans has unloaded on Mr Trump, describing him as ill-informed, under-prepared and ethically challenged.

"Personally driven by instinct and impulse, unhampered by knowledge or judgment, he has led an administration acting so far on the basis of postures rather than policies," Mr Evans will say in a speech today to the National Press Club.

"While the commentariat is beginning to find some comforting early signs that the adults are regaining charge of foreign policy, anyone betting on this administration delivering consistent, coherent, constructive and decent outcomes over the next four years is making a very big gamble indeed."

Mr Evans, who was foreign minister in the Hawke and Keating governments, wants Australia to have a long think about its alliance with the US.

"My own answer to the dilemma of how Australia should respond to all of this is: less United States, more Asia, and more self-reliance," he said.

While Mr Evans agreed Australia gained a lot from the alliance, particularly in intelligence and military terms, he believed support for the US should be much less reflexive.

"'Whither thou goest' might be good theology, but it is not great foreign policy for a country that values its independence and wants international respect," he said.

"We should have learned that lesson after Iraq in 2003, but recent events suggest not.

"Take the immediate, absolute and unconditional support for the unilateral missile strike in Syria — it was certainly defensible, but has a number of very problematic dimensions."

Australia 'capitulates' to the US

Mr Evans also outlined some of his concerns yesterday during a foreign policy discussion convened by the Melbourne-based Centre for Policy Development and the Australian National University, of which he is Chancellor.

He is particularly angry about what he says is Australia's "absolute capitulation to US pressure" not to take part in international efforts towards nuclear disarmament.

"My own experience strongly suggests saying 'no' to the US when our national interests are manifestly different, makes for a much healthier and productive relationship than one of craven dependence," he said.

Australia's relationship with the United States has been strained by tensions over the deal, struck with the Obama administration, to resettle refugees on Manus Island and Nauru in the US.